| Budget Amount *help |
¥3,900,000 (Direct Cost: ¥3,900,000)
Fiscal Year 1998: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1997: ¥3,100,000 (Direct Cost: ¥3,100,000)
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| Research Abstract |
It is acknowledged that the major cause of N-methyl carbamates and organophosphates resistance in the green rice leafhopper, Nephotettix cincticeps Uhler, is a reduced sensitivity of acetylcholinesterase(AChE) to these insecticides. In this study, a simple biochemical monitoring method for resistance by assaying sensitivity of AChE of individual insects to insecticides was established. And this method was found to be useful for the monitoring of N-methyl carbamamates and organophosphates resistance in the green rice leafhopper. By using this monitoring method, we found that the combination of N-methyl carbamate and monocrotophos (OP) showed negatively correlated cross resistance in the green rice leafhopper at in vitro AChE inhibition. However, this unique relation was not found by the bioassay. Thus, N-methyl carbamate resistance gene of the field strain was introduced to a susceptlble strain, and we bred Rmc strain. Using a susceptible and Rmc strains, we found that there is a negatively correlated cross resistance between the two insecticides. The cause we could not find the negatively correlated cross resistance in the field strain by bioassay was found to be an increased aliesterase(AliE) which sequestered monocrotophos in resistant strain. By pair mating of various strains, we found that the GRLH possess 6 isozymes of AChE.We tried to isolate and purify AChE of heads from a susceptible and resistant strains. We could purify AChE about 3000 times. There was a clear difference between these two AChEs in biochemical characters. We are going to clarify molecular mechanism of negatively correlated cross resistance at AChE inhibition.
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